The study addresses the question of whether adding a Contingency Management (CM) approach, in which adolescents are provided with a monetary incentive for providing clean urine, enhances the efficacy of two research-proven interventions for adolescent substance use. Specifically, the investigators compare if Functional Family Therapy (FFT) and Motivational Enhancement/Cognitive Behavioral Therapy (MET/CBT) combined with CM are better than either intervention alone. The investigators also explore the extent to which the addition of CM increases the speed with which adolescents achieve abstinence as well as the durability of these effects over time. The inclusion of two distinct forms of therapy also permits the investigation of how the interventions achieve their effects on adolescent drug use (e.g., improvements in family functioning in FFT vs. improvements in drug avoidance and self-efficacy skills in MET/CBT).